Why arent Wolfire.com putting Overgrowth on Steam Greenlight? I'd think it would have a much better chance to get greenlit! And not so many people know about Owergrowth, so wouldnt putting it on Greenlight be an, also perfect, commercial?

No, because on steam you can get a hundred times more attention. I dont know what % steam takes from the price, but I'm sure that even if it was as high as 50% which it surely isnt, it would still be worth it.

problem is, overgrowth is still technically in early alpha, they said it will probably take a couple more years before the game is ready to be played commercially, but they do plan to put it on steam, and judging by how the game's fanbase is growing, it WILL be a big release.